P0442 on a 2016 Chevrolet Impala Eco Eassist

P0442 means the EVAP system could not hold pressure or vacuum during a leak test, but the leak is small.

Not your vehicle? See general P0442 info.

Most common causes on the 2016 Chevrolet Impala Eco Eassist

Ranked from 786 NHTSA owner complaints filed for this vehicle.

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1
EVAP vent valve stuck closed / restricted tank venting
Medium severity
A complaint describes the tank refusing to fill past about three-quarters capacity — a classic symptom of a stuck-closed EVAP vent valve or restricted vent line that can also trip small-leak EVAP codes.
Reported in 1 NHTSA complaint
Parts:EVAP vent valve
2
Emissions system fault flagged after an auto-stop stall
Low severity
One owner's dash displayed an emissions-control message tied to a stall coming out of auto-stop; not conclusively an EVAP leak, but it points at the emissions monitoring system as worth checking alongside the code.
Reported in 1 NHTSA complaint
3
Loose or damaged gas cap
Low severity
A cap that isn't sealing fully is the single most common trigger for a small EVAP leak code.
Common cause
Parts:gas cap
4
Failing EVAP canister purge valve
Medium severity
A purge valve that leaks at rest lets fuel vapor bleed past it, dropping system pressure enough to fail the small-leak test.
Common cause
Parts:purge valve
5
Cracked or brittle EVAP line
Medium severity
Heat- and age-cracked vapor lines are a frequent small-leak source, especially near the engine bay or under the tank.
Common cause
Parts:EVAP hose
6
Charcoal canister crack
Medium severity
A cracked or saturated canister can't hold vapor pressure, tripping a small-leak code during the EVAP monitor's test.
Common cause
Parts:charcoal canister
7
Rusted or corroded filler neck
Low severity
Corrosion can pit the filler neck enough to leak vapor slowly, especially where road salt is used.
Common cause
Parts:filler neck

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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0442 on your car still needs shop confirmation before any repair.

Common symptoms

Check engine light
Fuel smell near vehicle
Usually drives normally
Hard start after fueling in some cases

What to check before replacing parts

Tighten and inspect the gas cap

Look for: A cap that doesn't click to full tightness, has a visibly cracked or flattened seal, or is simply missing is the single most common cause of a small EVAP leak — rule it out first.

Smoke-test the EVAP system

Look for: Because this is a small leak, expect only a thin wisp of smoke or a faint hiss at one spot (a hose, seam, or valve) rather than an obvious cloud — look closely and take your time.

Check purge valve sealing

Look for: A purge valve that doesn't hold vacuum when commanded closed lets a small amount of air bleed through, which the system reads as a leak during its self-test.

Inspect hoses near the tank and engine bay

Look for: Look for small cracks, soft/collapsed spots, or a hose that has pulled loose slightly at a fitting — any of these can leak just enough to trip a small-leak code without an obvious fuel smell.

Verify vent valve operation

Look for: A vent valve that doesn't seal fully when commanded closed prevents the system from holding vacuum during its self-test, which reads as a small leak even with no physical leak in the hoses.

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Matching symptoms

Check Engine Light